Bolt-action

A bolt-actionfirearm is typically a rifle (although they also used to make bolt-action shotguns) in which the opening and closing of the breech is controlled manually by a bolt.

Typically, the bolt consists of a tube of metal inside of which the firing mechanism is housed, and which has at the front or rear of the tube several metal knobs, or "lugs", which serve to lock the bolt in place. The operation can be done via a rotating bolt, a lever, or a number of systems. For example, one setup is a straight-pull design that use a rotating bolt, such as the German Blaser R93 rifle. Straight-pull designs have seen a great deal of use, though manual turn-bolt designs are what is most commonly thought of in reference to a bolt-action design due to the type ubiquity. As a result the bolt-action term is often reserved for more modern types of rotating bolt-designs when talking about a specific weapon's type of action, however both straight-pull and rotating bolt rifles are types of bolt-action rifles. Lever-action and pump-action weapons must still operate the bolt, but they are usually grouped separately from bolt-actions that are operated by a handle directly attached to a rotating bolt.

On used bolt-action firearms, especially, the headspace should be checked prior to shooting, to ensure that the spacing is correct to prevent over-stressing chambers and cartridge brass. Some bolt-action rifles, such as the Lee-Enfield SMLE, have a series of different length bolts available to extend the service life of the rifle, for taking up any wear of the bolt and chamber occurring from long years of service.

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Most bolt-action firearms are fed by an internal magazine loaded by hand, by en bloc, or stripper clips, though a number of designs have had a detachable magazine or independent magazine, or even no magazine at all, thus requiring that each round be independently loaded. Generally, the magazine capacity is limited to three to ten rounds, as it can permit the magazine to be flush with the bottom of the rifle, reduce the weight, or prevent mud and dirt from entering. A number of bolt-actions have a tube magazine, such as along the length of the barrel. In weapons other than large rifles, such as pistols and cannons, there were some manually operated breech loading weapons. However, the Dreyse Needle gun was the first breech-loader to use a rotating bolt design. Johann Nicholas von Dreyse's rifle of 1838 was accepted into service by Prussia in 1841, which was in turn developed into the Prussian Model 1849. The design was a single-shot breech loader, and had the now familiar arm sticking out the bolt to turn and open the chamber. The entire reloading sequence was a more comple

Russian Nagant rifle

x procedure than later designs, however, as the firing pin had to be independently primed and activated, and the lever was only used to move the bolt.

Bolt action firearms have earned a reputation for being more powerful than any semi automatic rifle. They are also far easier to accurize than semi-automatic firearms because a semi-auto has far more moving parts than a bolt action, gases at different pressures bled and diverted, and a host of spring tensions and sliding surfaces, it's just plain complicated to accurize a semi-auto and keep it firing at match-grade quality. For this reason, bolt actions are still the choice of many target shooters and snipers. This is true because of the way that bolt action rifles close the chamber. When a bullet fires inside the chamber, the force from the explosion is completely directed at propelling the bullet down the barrel (In an autoloader, part of the energy is used to cycle the action). Also, a bolt action's only moving parts when firing are the pin and spring. Since it has fewer moving parts and a small lock time, it has less of a chance of being thrown off target and less of a chance to jam. Finally, since the spent cartridge has to be manually removed instead of automatically ejected, it helps a sniper remain better hidden, since not only is the cartridge not flung into the air and to the ground, possibly giving away the sniper's position, but the cartridge can be removed when most prudent, allowing the sniper to remain still until reloading is tactically feasible. Bolt actions are also easier to operate from a prone position than other manually repeating mechanisms and work well with box magazines which are easier to fill and maintain than tubular magazines. However, there's been enough accumulated experience in tuning semi-autos that a modern semi-auto can be as accurate as any bolt action if well made.

Some disadvantages of the bolt action is that it is the slowest of all the major manual repeating mechanisms as it requires four distinct movements (as opposed to 2 for lever action and pump action firearms) and requires that the trigger hand leave the gun and regrip the weapon after each shot, usually resulting in the shooter having to realign his sight and reacquire the target for every shot. It is also not ambidextrous.

Throughout the 1800s breech-loading bolt-actions continued to develop following a steady progression, seeing widespread adoption and continual improvements in design. World War I marked the height of the type's use though automatic loading designs were introduced during the war.

During the build up prior to World War II, the military bolt-action rifle began to be superseded by the semi-automatic rifle and later assault rifles, though it remained the primary weapon of some (mostly Russian) infantry for the duration of the war. The bolt-action is still common today among sniper rifles, as the design has potential for superior accuracy, reliability, lesser weight, and the ability to control loading over the faster rate of fire that alternatives allow. There are however, many semi-automatic sniper rifle designs, especially in the designated marksmen role.

Today, bolt-action rifles are chiefly used as hunting rifles. These rifles can be used to hunt anything from vermin, to deer, to large game, especially big game caught on a safari, as they are adequate to deliver a single lethal shot from a safe distance.

Bolt-action shotguns are considered a rarity among modern firearms, but were formerly a commonly used action for .410 entry-level shotguns, as well as for low-cost 12 gauge shotguns. The XM26 Lightweight Shotgun System (LSS) is the most advanced and recent example, which may hold the distinction of being the first bolt-action shotgun to be used in military service. Although used limitedly and not officially adopted by US military, the XM26 is well-liked by soldiers issued with them in Afghanistan, being able to attach themselves to M-16 rifles or M4 carbines to increase the close-range firepower needed by infantrymen. Mossberg 12ga bolt-action shotguns were briefly popular in Australia after the 1997 firearms law changes

There are three major bolt action system designs: the Mauser system, the Lee-Enfield system, and the Mosin-Nagant system. Both differ in the way the bolt fits into the receiver, how the bolt rotates as it is being operated, the number of locking lugs holding the bolt in place as the gun is fired, and whether the action is cocked on the opening of the bolt (as in the Mauser system) or the closing of the bolt (as in the Lee-Enfield system).

The Mauser bolt system was introduced in the Mauser Gewehr 98 and is the most common bolt action system in the world, being in use in nearly all modern hunting rifles and the majority of military bolt-action rifles until the middle of the 20th century (besides the Mauser K98, the Mauser bolt system was also used in the American M1903 Springfield rifle, the Japanese Arisaka Type 38 and Type 99 rifles, and the Anglo-American M1917 Enfield). The Mauser system is stronger than that of the Lee-Enfield because of the third locking lug present at the rear of the bolt, and is able to handle higher pressure cartridges (i.e. "Magnum" calibre centrefire rifle cartridges), unlike the Lee-Enfield or Mosin-Nagant actions. The Mauser system, due to its "cock on opening" operation (the upward rotation of the bolt when the rifle is opened cocks the action) has a slower rate of fire than the "cock on closing" systems used in the Lee-Enfield.

The Lee-Enfield bolt action system was introduced in 1889 with the Lee-Metford and later Lee-Enfield rifles (the bolt system is named after the designer and the Royal Small Arms Factory at Enfield), and is a "cock on closing" action in which the forward thrust of the bolt cocks the action. This allows for a much faster rate of fire (See Mad Minute), but the system is unsuitable for use with modern "Magnum" calibre centerfire rifle cartridges. Interestingly, the Lee-Enfield bolt system features a removable bolthead, which allows the rifle's headspace to be adjusted by simply removing the bolthead and replacing it with one of a different length as required. In the years leading up to WWII, the Lee-Enfield bolt system was used in numerous commercial sporting and hunting rifles manufactured by such firms in the UK as BSA, LSA, and Parker-Hale, as well as by SAF Lithgow in Australia. Vast numbers of ex-military SMLE Mk III rifles were sporterised post-WWII to create cheap, effective hunting rifles, and the Lee-Enfield bolt system is used in the M10 and No 4 Mk IV rifles manufactured by Australian International Arms.

The Mosin-Nagant action differs from the Mauser and Lee-Enfield actions, in that it has a separate bolthead which rotates with the bolt and the bearing lugs, in contrast to the Mauser system where the bolthead is a non-removable part of the bolt are a single piece and rotate as such, or the Lee-Enfield system where the bolthead remains stationary and the bolt body rotates. The Mosin-Nagant bolt is a somewhat complicated affair, but is extremely rugged and durable. Like the Lee-Enfield bolt system, the Mosin-Nagant system is not suitable for use with modern "Magnum" calibre centrefire rifle cartridges. Although the bolt system is not employed in any commercial sporting rifles, the Mosin-Nagant rifle is the most numerous bolt-action rifle ever produced and large numbers of them have been sporterised for use as hunting rifles in the years since WWII.

Some rifles- such as the Swedish Mauser and the Pattern 1914 Enfield use a hybrid of the two systems.
The Model 96 and Model 38 Swedish Mausers, for example, use a Mauser bolt which is of a "cock on closing" closing design (giving it a faster rate of fire than the Mauser K98 or the M1903 Springfield, but still not quite as fast as the Lee-Enfield), whereas the Pattern 1914 Enfield uses a system whereby the action is half-cocked as the bolt is opened, with the forward thrust of the bolt on reloading fully cocking the rifle.